Hearing assistance devices, such as hearing aids, are designed to provide signal processing that assists the hearing of a wearer. In the case of hearing aids, the wearer typically has hearing loss which is characterized by an audiogram which shows where such loss occurs as a function of frequency and the extent of the hearing loss. Hearing aids provide, among other things, customizable gain as a function of frequency to compensate for that hearing loss. The process of customizing a hearing aid to restore hearing to a more natural level is called “fitting.” One way to determine if the appropriate settings are employed in the fitting process is to monitor the sound pressure level (SPL) at or near the tympanic membrane and discomfort of the individual of the wearer to determine that the proper gain has been applied to the wearer of the device. Such measurements can present a danger of damage to the tympanic membrane if not properly performed. These measurements may also require complicated microphone measurements within the patient's ear canal that are prone to error. Such methods can distort the natural soundfield present in the ear canal or interfere with the normal operation of the hearing aid during test, especially at higher frequencies of the hearing spectrum.
Recently, researchers have given much attention to determining whether individuals with hearing loss can benefit from extended high-frequency information. While some of these studies have shown improved sound quality or speech understanding by increasing the bandwidth beyond 6 kHz, there remain several challenges that must be overcome before extended bandwidth hearing aids can become a clinical reality.
Thus, there is a need in the art for improved measurements of sound pressure level. Such measurements should be accurate at high frequencies and should be straightforward to perform for accurate measurement of sound pressure level near the tympanic membrane.